Cook the Rice: In a small saucepan, bring the rice and water to a boil. Reduce heat; simmer, covered, until rice is tender, 35-40 minutes.
Preheat the Oven: Preheat your oven to 350°F (175°C).
Assemble the Casserole: In a large bowl, combine the cooked rice, black beans, corn, diced tomatoes, salsa, sour cream, 1 cup cheese and spices. Transfer the mixture to a 9×13-inch baking dish coated with cooking spray.
Bake: Cover the dish with foil and bake for 30 minutes. Remove the foil, sprinkle the casserole with remaining shredded cheese, and bake uncovered for an additional 5-10 minutes, or until the cheese is melted and bubbly.
Rest and Serve: Let the casserole stand for 5-10 minutes before serving. Garnish with your favorite toppings like avocado, tomatoes, cilantro, or sour cream.